Recent advances in single-particle cryogenic-electron microscopy have facilitated an exponential growth in the number of membrane protein structures determined to close to atomic resolution. Nevertheless, despite improvements in microscope hardware, cryo-EM software and sample preparation techniques, challenges remain for structural analysis of small-sized membrane proteins (i.e.<150 kilodalton). Here we discuss recent examples of structures of macromolecules from this category determined by cryo-EM. We analyze the underlying difficulties, the enabling technologies such as the use of antibody fragments to gain size and provide fiducials for particle alignment, and the unresolved issues like dislocation of complexes at the air-water interface. Finally, we briefly highlight the biological relevance of some of these success stories, and our predictions for the future.

中文翻译：

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小膜蛋白的冷冻电子显微镜分析。


单颗粒低温电子显微镜的最新进展促进了接近原子分辨率的膜蛋白结构数量的指数增长。然而，尽管显微镜硬件、冷冻电镜软件和样品制备技术有所改进，小尺寸膜蛋白（即<150 kilodalton）的结构分析仍然面临挑战。在这里，我们讨论通过冷冻电镜测定的此类大分子结构的最新示例。我们分析了潜在的困难、使能技术（例如使用抗体片段来获得尺寸并为颗粒排列提供基准）以及未解决的问题（例如空气-水界面处复合物的错位）。最后，我们简要强调了其中一些成功案例的生物学相关性，以及我们对未来的预测。